This invention relates generally to computed tomography (CT) imaging, and more particularly to reliable cardiac imaging using a CT system.
The dynamic nature of a heart, and temporal and spatial resolution requirements for reliable diagnosis, make cardiac imaging a challenging task for CT technology. Specifically, as a CT gantry rotates, the heart continues to beat and move, and projection data is collected at varying cardiac phases. Since projection data cannot be acquired instantaneously, so that the cardiac phase of the heart is known for each projection data set, electrocardiograph (EKG) data is collected to correlate, or xe2x80x98tagxe2x80x99, CT projection data with cardiac phase information. The cardiac phase information is obtained by dividing each cardiac cycle of the EKG signal into sections that represent the different cardiac phases. One cardiac cycle within an EKG signal is understood to be represented by the part of the signal plotted from one R peak to the next R peak, i.e., the RR interval.
Typically, cardiac phases are determined by temporally dividing the RR interval in a linear fashion. There is an assumption that the duration of events in the RR interval scale linearly when the heart rate changes. However, when the heart rate changes, the different cardiac phases do not change linearly. Thus, temporal based, or linearly scaled, cardiac phase determination is not always accurate as the heart rate changes.
Projection data acquired from multiple rows of detectors are pre-processed to tag each view with z-location information and with the cardiac phase information. Projection data are selectively combined from multiple cardiac cycles for image reconstruction at specified z-locations and cardiac phases. Inaccuracies due to heart rate changes, however, impact the temporal and spatial resolution of the resulting image.
In one aspect, a method is provided for reconstructing an image of a beating heart. The method includes decomposing at least one electrocardiogram (EKG) RR interval such that the EKG RR interval is separated into constituent parts. Furthermore the method includes tagging projection data with cardiac phase information based on the decomposition, and reconstructing an image using the tagged data.
In another aspect, a system is provided for reconstructing an image of a beating heart. The system includes an electrocardiogram (EKG) device, a computed tomography (CT) device electrically coupled to the EKG device, and a processor electrically coupled to at least one of the EKG device and the CT device. Furthermore, the system is configured to decompose at least one electrocardiogram (EKG) RR interval, determine cardiac phase information based on the decomposition, and reconstruct an image using the phase information.
In yet another aspect, a computer readable medium encoded with a program executable by a computer, is provided for reconstructing images of a beating heart utilizing data gathered using a computed tomography (CT) device and an electrocardiogram (EKG) device. The program instructs the computer to decompose at least one EKG RR interval into at least one of a P wave, a Q wave, a R wave, a S wave, and a T wave, and tag projection data with cardiac phase information based on the decomposition.
In still another aspect, a method is provided for determining cardiac phase information used to reconstruct an image of a beating heart. The method includes decomposing at least one EKG RR interval and determining cardiac phase information based on the decomposition.